This application claims the benefit of priority from Japanese Patent Application No. 2000-275030, filed on Sep. 18, 2000, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an image forming apparatus, which forms the image on a substrate using a liquid developer containing toner particles and a solvent. The present invention also relates to a developing system which can be attached to an image forming apparatus and uses the liquid developer.
2. Discussion of the Background
An image forming apparatus using a liquid developer has promising advantages which an image forming apparatus using dry toner does not have. One advantage arises due to the fact that the liquid developer contains a carrier solvent and toner particles, which have an average particle size in the sub-micrometer range, much smaller than size of dry tone particles, whereby it is high image quality is preferably obtained. The liquid developer also decreases the amount of toner particles needed to develop images, while maintaining high image density. Therefore, liquid toners are economical in addition to enabling realization of fine texture printed images. The liquid developer also allows fixing of a developed image onto a final substrate at relatively low temperature and therefore is preferable from the standpoint of energy conservation.
On the other hand, the image forming apparatus using liquid developer has several features which has rendered its use second to the image forming apparatus using dry toner. One such feature is difficulty in handling the carrier solvent of the liquid developer. The solvent usually contains insulating liquid hydrocarbon, such as xe2x80x9cIsoperxe2x80x9d sold by Exon. However, the solvent may evaporate at room temperature and produce some odor. Therefore, the liquid developer has not typically been used in an office environment, but instead has been applied to special purposes uses, such as large-sized machines for professional use.
The image forming apparatus using the liquid developer has a developing unit and a latent image retaining body. The developing unit usually has a developing roller, which applies the liquid developer onto a surface of the latent image retaining body at a developing region and is supported via sleeve rings to keep a developing gap from the surface of the image retaining body. The developing roller provides the liquid developer to fill the developing gap and also maintains a certain electric potential difference from the surface of the latent image retaining body to develop the latent image by moving the toner particles in the solvent by electrophoresis.
The developing roller and the latent image retaining body push one another via the sleeve rings to maintain the appropriate developing gap. The image forming apparatus usually has four developing units to obtain multi color image and therefore the latent image retaining body receives pressures from four developing units. The four colors are usually yellow, magenta, cyan, and black.
A solvent in the developing image on the latent image retaining body may be removed by a solvent removing unit and the solvent removed image is transferred to an intermediate transfer body, which usually has an elastic surface layer and is pressed against the latent image retaining body at a transfer station. The image on the intermediate transfer body is transferred to a paper, which is caught between the intermediate transfer member and a backup roller.
The intermediate transfer body is pressed at a nip region against the latent image retaining body with high pressure; therefore the latent image retaining body receives the pressure at the nip region. When the latent image retaining body is a drum, its shaft keeps the drum rotating during its operation and receives the high pressure.
An object of the present invention is to provide an image forming apparatus and an image developing system, which use a liquid developer, and reduce leakage of the solvent or the solvent vapor of the liquid developer, therefore is appropriate for the general use in offices and homes.
In various aspects, embodiments of the present invention provide image forming apparatuses, which form an image on a substrate by using a liquid developer containing toner particles and a solvent.
According to a first aspect, one embodiment of the present invention provides an image forming apparatus, which includes a latent image retaining body including a photosensitive layer, a developing unit disposed adjacent to the latent image forming unit, a solvent reducing unit disposed adjacent to the developing unit, a transfer unit disposed adjacent to the latent image retaining body and the solvent reducing unit, and an inner case comprising a frame and a portion defining an opening of the frame. The developing unit faces the latent image retaining body and is configured to provide the liquid developer on the image retaining body. The solvent reducing unit is disposed adjacent to the developing unit, facing the latent image retaining body, and configured to reduce the solvent of the liquid developer on the latent image retaining body. The inner case supports the latent image retaining body, the developing unit, and the solvent reducing unit inside of the frame, and the portion defining the opening is arranged adjacent to the transfer unit.
In a third aspect, one embodiment of the present invention provides an image forming apparatus, which includes rotatable latent image retaining body, a developing unit arranged adjacent to the latent image retaining body, and a transfer surface contacting the latent image retaining body at a transfer station. The developing unit has a developing gap from the latent image retaining body at a developing region, contacts the latent image retaining body at both edges adjacent to the developing region, and is configured to provide a first pressure to the latent image retaining body. The transfer surface is configured to provide a second pressure to the latent image retaining body. The directions of the first and second pressures are antiparallel, and weights of the first and second pressures are substantially equal so as to cancel each other out.
In various aspects, embodiments of the present invention provide developing systems, which can be attached to an image forming apparatus and develop an image by using the liquid developer containing toner particles and a solvent.
In a fourth aspect, the present invention provides a developing system, which comprises a latent image retaining body including a photosensitive layer, a developing unit facing the latent image retaining body, a solvent reducing unit disposed adjacent to the developing unit facing the latent image retaining body, and an inner case including a frame and a portion defining an opening of the frame. The developing unit is configured to apply the liquid developer on the image retaining body. The solvent reducing unit is configured to reduce the solvent of the liquid developer on the latent image retaining body. The inner case supports the latent image retaining body, the latent image forming unit, the developing unit, and the solvent reducing unit inside of the frame. The portion defining the opening is arranged adjacent to the solvent reducing unit.
In a fifth aspect, one embodiment of the present invention provides a developing system, which includes a rotatable latent image retaining drum, a developing unit arranged adjacent to the latent image retaining drum, a transfer body contacting the latent image retaining drum at a transfer station, and a case holding the latent image retaining drum, the developing unit, and the transfer body. The developing unit maintains a developing gap from the latent image retaining drum at a developing region, contacts the latent image retaining drum at both edges adjacent to the developing region, and is configured to provide a first pressure to the latent image retaining drum. The transfer body is configured to provide a second pressure to the latent image retaining drum at the transfer station. Directions of the first and second pressures are antiparallel, and weights of the first and second pressures are substantially equal so as to cancel each other out.